Sophiris Bio has completed its investigation into the death of a patient that halted additional dosing in a trial of its lead candidate topsalysin two months ago, finding its procedure for localized prostate cancer was unlikely to be the cause.
Sophiris’ stock was up 30% on the news, after dropping precipitously in June. The company said it has notified regulatory authorities in the U.S. and the U.K., where the open-label phase 2b study is being conducted.
Topsalysin, a transmembrane, pore-forming protein, was genetically modified to be activated only by enzymatically active prostate-specific antigen, with the goal of eroding localized prostate cancer lesions while avoiding complications.
Additional doses in the study were stopped after the patient died on the same day he received his second intraprostatic dose of the drug, at six months after his initial treatment. Only patients that had not seen an adverse event linked to the drug could receive an additional dose, and they must have previously shown responses to treatment, the company said at the time.
Following a review of the autopsy report, hospital records and negative serology results for acute hypersensitivity, Sophiris and the investigator linked the cause to sudden cardiac death, possibly due to an arrhythmia, with the patient having multiple risk factors.
The company now plans to move forward with its phase 3 study design based on previous data, Sophiris President and CEO Randall Woods said in a statement. Woods also expects to report complete safety and efficacy data from the phase 2b study before the end of the year, including results from 10 of the trial’s 38 patients who received a second dose of topsalysin.
In June, interim results from a single dose showed 29% of 35 evaluated patients showed sustained clinical responses after six months, including biopsies showing no detectable or clinically insignificant tumors. No new hypersensitivity or serious systemic safety signals were reported.
Before that, topsalysin met its endpoints in benign prostatic hyperplasia in a 2015 phase 3 study of 479 patients, improving symptoms over 12 months.